Synthesis of 1,2,4,-Triazolo[4',3':1,6]pyridazino[4,5-b]quinoline Derivatives

This paper reports the synthesis of 10‐phenyl‐2H‐pyridazino[4,5‐b]quinoline‐1‐thione 10 and its further transformation into the hitherto unknown 12‐phenyl‐1,2,4‐triazolo[4′,3′:1,6]pyridazino[4,5‐b]quinoline 4. 3‐Carbethoxy‐2‐dichloromethyl‐4‐phenylquinoline 8 was reacted with hydrazine to give 9 which in turn was transformed by the Lawesson Reagent into the corresponding thione 10. On treating 10 with anhydrous hydrazine, 11 was obtained and subsequently cyclized in the presence of formic or acetic acids to afford the tetracyclic derivatives 4a and 4b, respectively, in satisfactory yields. When 3‐carbethoxy‐2‐chloromethyl‐4‐phenylquinoline 5 was reacted with hydrazine, compound 7 was the sole isolated product. Copyright © 1990 Journal of Heterocyclic Chemistry